Portable electronic devices, such as tablet computers, need to be held by users or placed on a table for being browsed the screen. However, when the portable electronic device is held by the user for a long time, the user may become tired. When the portable electronic device is placed on the table, the portable electronic device needs support, such as some books, on its back for a right angle to be viewed hands-free. For conveniently using the portable electronic device, a holder with multiple angles of adjustment is needed.